Abstract

Steady-state accommodation responses were measured in both eyes as a function of vergence angle and direction of lateral gaze. The measurements were made with a binocular laser optometer. Small speckle patterns were used as fusional stimuli in an otherwise dark field. These patterns have the advantage of providing no blur stimulus to accommodation. Convergence accommodation for vergence angles ranging from 0 to 25 deg was measured for lateral- gaze angles of +32, -32, and 0 deg. The average accommodation of the two eyes was linearly related to vergence angle over the observer's accommodative range but was independent of the angle of lateral gaze. The mean convergence accommodation/convergence ratio for three subjects, in diopters per meter-angle, was 0.9. Our measurements of convergence accommodation using laser-speckle targets are in good agreement with previous studies that used small pupils. Accommodation responses for binocular viewing of letters of a Snellen chart were also measured. When luminance was educed, night myopia was observed. No similar effect was found for convergence accommodation. Accommodation to a dim target corresponded closely to the convergence accommodation.

We measured accommodation responses to speckle targets under monocular viewing conditions as a function of dioptric power of lenses (from +1 to-6 diopters) placed in front of the eye. When accommodation was plotted as a function of lens power, the slope of the line through the data was nearly zero (+0.02).

This allows for the wavelength of the red He–Ne laser light, which is 632.8 nm.

If IPD represents the interpupillary distance in meters, the CA/C ratio in diopters/meter-angle is given by IPD × 57.3 × CA/C/ diopters/deg. However, this is only an approximate equivalence. For large version and vergence angles, dioptric distance in meter-angles is no longer closely proportional to vergence. For asymmetric convergence there is ambiguity because of the differences in the right- and left-eye distances from the fixation point.

Vision. Res. (1)

Other (7)

We measured accommodation responses to speckle targets under monocular viewing conditions as a function of dioptric power of lenses (from +1 to-6 diopters) placed in front of the eye. When accommodation was plotted as a function of lens power, the slope of the line through the data was nearly zero (+0.02).

It should also be pointed out that if all subjects have lines with equal (and perhaps steep) slopes but different intercepts, the averaged data produce a line of smaller slope.

This allows for the wavelength of the red He–Ne laser light, which is 632.8 nm.

If IPD represents the interpupillary distance in meters, the CA/C ratio in diopters/meter-angle is given by IPD × 57.3 × CA/C/ diopters/deg. However, this is only an approximate equivalence. For large version and vergence angles, dioptric distance in meter-angles is no longer closely proportional to vergence. For asymmetric convergence there is ambiguity because of the differences in the right- and left-eye distances from the fixation point.

F. C. Donders, On the Anomalies of Accommodation and Refraction of the Eye (New Sydenham Society, London, 1864).